Thin people may be due to anorexia and picky eating and other physiological reasons, can be through a change in dietary habits, eat more high-calorie, high-protein food to gain weight; can also be due to gastrointestinal disorders and so on, this is the need to seek medical treatment. You can gain weight by changing your dietary habits, eating more eggs, milk, grains, nuts and other high-nutrition, high-fat or high-protein foods to ensure that the nutrition is comprehensive, while increasing energy intake, so as to achieve the purpose of gaining weight. However, fattening can eat more, but do not eat indiscriminately, you should maintain food diversity and nutritional balance of the increase, to prevent increasing the burden on the stomach and intestines. At the same time combined with moderate training, increase muscle mass, also conducive to weight gain. Thin body size may be related to poor digestion, consumptive diseases (such as malignant tumors, etc.), hyperthyroidism and other diseases, which can be alleviated by timely consultation, identifying the cause of the disease and following the doctor’s instructions for treatment, so as to alleviate the situation of low body weight.